Accuphase P-300, worth upgrading?

I recently acquired an Accuphase P-300 power amp and my question is about rebuilding it. I haven't really listened to it yet, other than hooking it up to see if it worked and it seems fine. The amp is in mint condition but it is close to 40 years old so I am sure it needs serviced and I would like to upgrade it to sound as good as it can, if that is practical. If I were to refurbish this amp just how good can it be? What price range in a current amp would it compare to? I have $600 in the amp. Who would you send it to to bring it up to speed? Any thoughts or suggestions are very much appreciated.
My advice is to use components as close as possible to authentic and NOT to try to upgrade if you want to keep with Accuphase sound which is already perfect.
Meanwhile enjoy your amp but not overload it at this point.
Any change will alter the sound, it depends on what you think of the sound you are getting now. Try listening to it for a while before you do anything. The caps would be the place to start if you want to modify, stay with the same values you have now. Much better resistors are now available but again the sound will change.
Hi Wemfan

Here is one place I was considering to fix up the Accuphase gear I have.

They have listings on other sites.

Accuphase P-300
I believe Accutech in SoCal would be the best resource to restore the P-300. If I owned one that is where I would send it.
The only way you will change the sound of your amp in rebuilding is by improving it. Especially an amp as old as yours. Components have come a long way since 40 years ago. The only limiting factor is the competence of the one doing the work. This amp is by no means "perfect" sounding at this age. Therefore you have no reference point anyway. I would recommend Roy A. Esposito of Sounds like New. He is one of the engineers who designed and built the Acoustat TNT 200. He's currently rebuilding a second 200 for me with a mono switch as with the first. The sound of the one I have is state of the art. It would probably run about 4-600.00
the suggestion to change caps is a good one. there are a number around which will give the amp a more full-bodied presentation.

if i had a solid state amp, i would have it modified so that it resembled the sound of classic tubes. i'd change caps, resistors, the bias and if possible, introduce some additional even order harmonic ditortion.

i have never heard a solid state amp that is listenable above 1000 hz. the upper mids on up create listener fatigue after a while.
Mrtennis, unfortunately I can't relate SS fatigue above 1kHz with mods and upgrades to it. There's no general rule of thumb on that, but particular to Accuphase P-300 many folks, owners would NOT suggest any upgrades and keep it as original as possible matching all values replaced circuit elements.

Your task is to find any owner of any accuphase amp that gets fatigue post 1000Hz.

I will be providing service to E202 this weekend and charged $250 for labor only having all parts provided by owner. To my knowlege the parts match ones on the circuit board. My job will include reapplying new solder(purchased by client), cleaning and reconditioning all switches and potentiometers, repairing a volume control, cleaning faceplate, replacing filter and other DC caps and cleaning all RCA sockets and binding posts. There's a shop in Long Island(NY) that would do that for $450 including all circuit elements replaced and serviced. $680 seems to be a professional rip-off.